NsdManager

Class Overview

The Network Service Discovery Manager class provides the API to discover services on a network. As an example, if device A and device B are connected over a Wi-Fi network, a game registered on device A can be discovered by a game on device B. Another example use case is an application discovering printers on the network.

The API currently supports DNS based service discovery and discovery is currently limited to a local network over Multicast DNS. DNS service discovery is described at http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt

The API is asynchronous and responses to requests from an application are on listener callbacks on a seperate thread.

There are three main operations the API supports - registration, discovery and resolution.

                          Application start
                                 |
                                 |
                                 |                  onServiceRegistered()
                     Register any local services  /
                      to be advertised with       \
                       registerService()            onRegistrationFailed()
                                 |
                                 |
                          discoverServices()
                                 |
                      Maintain a list to track
                        discovered services
                                 |
                                 |--------->
                                 |          |
                                 |      onServiceFound()
                                 |          |
                                 |     add service to list
                                 |          |
                                 |<----------
                                 |
                                 |--------->
                                 |          |
                                 |      onServiceLost()
                                 |          |
                                 |   remove service from list
                                 |          |
                                 |<----------
                                 |
                                 |
                                 | Connect to a service
                                 | from list ?
                                 |
                          resolveService()
                                 |
                         onServiceResolved()
                                 |
                     Establish connection to service
                     with the host and port information

 

An application that needs to advertise itself over a network for other applications to discover it can do so with a call to registerService(NsdServiceInfo, int, NsdManager.RegistrationListener). If Example is a http based application that can provide HTML data to peer services, it can register a name "Example" with service type "_http._tcp". A successful registration is notified with a callback to onServiceRegistered(NsdServiceInfo) and a failure to register is notified over onRegistrationFailed(NsdServiceInfo, int)

A peer application looking for http services can initiate a discovery for "_http._tcp" with a call to discoverServices(String, int, NsdManager.DiscoveryListener). A service found is notified with a callback to onServiceFound(NsdServiceInfo) and a service lost is notified on onServiceLost(NsdServiceInfo).

Once the peer application discovers the "Example" http srevice, and needs to receive data from the "Example" application, it can initiate a resolve with resolveService(NsdServiceInfo, NsdManager.ResolveListener) to resolve the host and port details for the purpose of establishing a connection. A successful resolve is notified on onServiceResolved(NsdServiceInfo) and a failure is notified on onResolveFailed(NsdServiceInfo, int). Applications can reserve for a service type at http://www.iana.org/form/ports-service. Existing services can be found at http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml Get an instance of this class by calling Context.getSystemService(Context.NSD_SERVICE).

Summary

Nested Classes
interface	NsdManager.DiscoveryListener	Interface for callback invocation for service discovery
interface	NsdManager.RegistrationListener	Interface for callback invocation for service registration
interface	NsdManager.ResolveListener	Interface for callback invocation for service resolution

Constants
String	ACTION_NSD_STATE_CHANGED	Broadcast intent action to indicate whether network service discovery is enabled or disabled.
String	EXTRA_NSD_STATE	The lookup key for an int that indicates whether network service discovery is enabled or disabled.
int	FAILURE_ALREADY_ACTIVE	Indicates that the operation failed because it is already active.
int	FAILURE_INTERNAL_ERROR	Failures are passed with onRegistrationFailed(NsdServiceInfo, int), onUnregistrationFailed(NsdServiceInfo, int), onStartDiscoveryFailed(String, int), onStopDiscoveryFailed(String, int) or onResolveFailed(NsdServiceInfo, int).
int	FAILURE_MAX_LIMIT	Indicates that the operation failed because the maximum outstanding requests from the applications have reached.
int	NSD_STATE_DISABLED	Network service discovery is disabled
int	NSD_STATE_ENABLED	Network service discovery is enabled
int	PROTOCOL_DNS_SD	Dns based service discovery protocol

Public Methods
void	discoverServices(String serviceType, int protocolType, NsdManager.DiscoveryListener listener) Initiate service discovery to browse for instances of a service type.
void	registerService(NsdServiceInfo serviceInfo, int protocolType, NsdManager.RegistrationListener listener) Register a service to be discovered by other services.
void	resolveService(NsdServiceInfo serviceInfo, NsdManager.ResolveListener listener) Resolve a discovered service.
void	stopServiceDiscovery(NsdManager.DiscoveryListener listener) Stop service discovery initiated with discoverServices(String, int, NsdManager.DiscoveryListener).
void	unregisterService(NsdManager.RegistrationListener listener) Unregister a service registered through registerService(NsdServiceInfo, int, NsdManager.RegistrationListener).

[Expand] Inherited Methods

From class java.lang.Object Object clone() Creates and returns a copy of this Object. boolean equals(Object o) Compares this instance with the specified object and indicates if they are equal. void finalize() Invoked when the garbage collector has detected that this instance is no longer reachable. final Class<?> getClass() Returns the unique instance of Class that represents this object's class. int hashCode() Returns an integer hash code for this object. final void notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. final void notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. String toString() Returns a string containing a concise, human-readable description of this object. final void wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object. final void wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires. final void wait(long millis) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.